1. Field of the Invention
The present invention relates to an apparatus used in fabricating liquid crystal display (LCD) devices. More particularly, the present invention relates to a substrate bonding apparatus used in fabricating (LCD) devices.
2. Discussion of the Related Art
As the development of diverse types of information devices proliferate and become available to consumers, demands on displays used by the information devices have increased. To meet such demands, many types of flat panel display devices including Liquid Crystal Display (LCD) devices, Plasma Display Panels (PDP), Electro Luminescent Display (ELD), Vacuum Fluorescent Display (VFD), etc., are currently being developed and, in some instances, are actually employed as displays.
Among the various types of flat panel displays, LCD devices are commonly used as portable display devices. Due to their beneficial characteristics such as excellent picture quality (e.g., high resolution and luminance), light weight, thin profile, large display area, and low power consumption, LCD devices are commonly used in applications previously dominated by Cathode Ray Tubes (CRTs). Accordingly, LCD devices are commonly used as monitors of notebook computers, monitors of computers, as TVs capable of receiving and displaying broadcasting signals, etc.
Generally, LCD devices are fabricated according to liquid crystal injection or liquid crystal dispensing methods. Using related art liquid crystal injection methods, LCD devices are fabricated by bonding substrates together in a vacuum via sealant material, wherein the sealant material is patterned to define a liquid crystal injection hole. After being bonded, liquid crystal material is injected through the liquid crystal injection hole and between the bonded substrates. Japanese Laid Open Patent Nos. 2000-284295 (Japanese Patent Application 1999-089612) and 2001-005405 (Japanese Patent Application 1999-172903) can be understood to teach a related art liquid crystal dispensing method wherein liquid crystal material is dispensed directly onto a first substrate. Subsequently, the first substrate is bonded to a second substrate in a vacuum, wherein the dispensed liquid crystal material is arranged between the first and second substrates. Because the liquid crystal dispensing method dispenses liquid crystal material directly onto the first substrate prior to bonding, various time consuming steps (e.g., formation of the liquid crystal injection hole, injection of the liquid crystal, sealing of the liquid crystal injection hole, etc.), essential to the liquid crystal injection method, are not required. Accordingly, the liquid crystal dispensing method can be used to fabricate LCD devices in less time than the liquid crystal injection method. As a result, much research has been performed in developing apparatuses capable of fabricating LCD devices while implementing liquid crystal dispensing methods.
FIGS. 1 and 2 illustrate a related art substrate bonding apparatus for fabricating LCD devices according to a liquid crystal dispensing method.
Referring to FIGS. 1 and 2, a related art substrate bonding apparatus includes a frame 10, an upper stage 21, a lower stage 22, a sealant dispenser (not shown), a liquid crystal dispenser 30, an upper chamber unit 31, a lower chamber unit 32, chamber moving means, and stage moving means. The sealant dispenser and liquid crystal dispenser 30 are mounted at side positions of the frame 10. The upper chamber unit 31 can be selectively joined to the lower chamber unit 32. The chamber moving means includes a driving motor 40 for moving the lower chamber unit 32 to position S1, where sealant material and liquid crystal material can be dispensed onto a substrate, and to position S2, where substrates can be bonded together. The stage moving means includes a driving motor 50 for raising and lowering the upper stage 21 before, during, and after the substrates have been bonded. Having described the related art substrate bonding apparatus above, the process by which the related art substrate bonding apparatus fabricates an LCD device will now be described in greater detail below.
To fabricate an LCD device using the related art substrate bonding apparatus described above, a first substrate 51 is held by the upper stage 21 while a second substrate 52 is held by the lower stage 22, as shown in FIG. 1. Next, the chamber moving means moves the lower chamber unit 32, supporting the lower stage 22, to the position S1. Subsequently, sealant material and liquid crystal material are dispensed onto the second substrate 52 held by the lower stage 22. After sealant material and liquid crystal material are dispensed onto the second substrate 52, the chamber moving means moves the lower chamber unit 32 to position S2, as shown in FIG. 2, whereby the first and second substrates 51 and 52, respectively, can be bonded together. With the lower chamber unit 32 at position S2, the chamber moving means joins the upper chamber unit 31 to the lower chamber unit 32. Upon being joined, the upper chamber unit 31 and the lower chamber unit 32 define an interior space that encloses the upper and lower stages 21 and 22, respectively, and is sealed from an external environment by a sealing means (not shown). Using a vacuum means (not shown), the interior space is evacuated to create a vacuum. Within the evacuated interior space, the stage moving means lowers the upper stage 21 such that the first substrate 51, held by the upper stage 21, moves toward the second substrate 52, held by the lower stage 22. As the upper stage 21 descends, the first and second substrates 51 and 52, respectively, become bonded to each other, thereby completing fabrication of the LCD device.
Fabricating LCD devices using the related art substrate bonding apparatus, however, is disadvantageous because, the related art substrate bonding apparatus applies sealant and liquid crystal material to substrates supporting thin film transistors and color filter layers and bonds the two substrates together. Accordingly, the overall size of the related art substrate bonding apparatus can become excessively large. This is especially so when the related art substrate bonding apparatus is designed to fabricate large-sized LCD devices.
Moreover, a substantially high degree of alignment is required to position the lower chamber unit 32 and facilitate adequate bonding of the first and second substrates. However, since the lower chamber unit 32 must be re-positioned numerous times, such alignment can be extremely difficult to obtain and is an unduly time consuming process, lengthening the entire process of fabricating LCD devices.
Further, an imperfect seal can be formed between the joined upper and lower chamber units 31 and 32, respectively. As a result, air may leak or foreign materials may be introduced from the external environment into the interior space defined by the upper and lower chamber units and the substrates may become damaged during bonding, thereby creating a defective bond.
Still further, the related art substrate bonding apparatus described above is calibrated to bond substrates of a predetermined reference thickness. In practice, however, the actual thickness of substrates loaded into the related art substrate bonding apparatus often vary from the reference thickness. Accordingly, recalibrating the related art substrate bonding apparatus to adequately process substrates having an actual thickness different from the reference thickness can be difficult and consume excessive amounts of time.
Moreover, the related art substrate bonding apparatus often disposed sealant material onto the same surface of a substrate that contacts a substrate loader. Accordingly, sealant material can be deleteriously contaminated by foreign materials introduced by the substrate loader.
Lastly, while sealing means may be provided within the related art substrate bonding apparatus to seal the interior space from the external environment, the sealing means can wear, rendering it impracticable to adequately seal the interior space between the joined chamber units.